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Test Code LAB3524 TSH Reflex to Free T4 Level 

Clinical System Name

TSH Reflex to Free T4 Level 

Sample Requirements

Specimen: Whole blood

Container(s): Gold SST, Red, Gold Microtainer, Dark Green/Sodium Heparin, Lt. Green/Lithium Heparin Microtainer, Lavender/EDTA

Preferred Vol: 2.0 mL

Minimum Vol: 1.0 mL

 

Processing Instructions

Reject due to: 

Spin: Y

Aliquot: Y

Temp: 2-8 C

Storage location: CPA refrigerator, FrigD rack. Serum should be removed from separator for storage.

Note: Minimum volume of 1.0 mL may be shared with TSH, T4, free T3, and free T4.

 

Off-site collection: Spin blood. Transfer serum to plastic aliquot container. Refrigerate.

Stability

Specimen Type Temperature Time
gel separator with serum Refrigerated 24 h
separated serum Room temp 2 h
  Refrigerated 7 d
  Frozen -20 C 6 m

 

Performing Laboratory

Seattle Children's Laboratory    

Department

Department:  Chemistry

Location: Chem West

Phone Number:  (206) 987-2617

 

 

 

Synonyms

TSH Rfl FT4

TSH Fl FT4

TSH Rflx FT4

Availability

STAT Performed TAT
Y* M-Sa, day shift 1-3 d

*For STAT requests, outside of testing availability, attending providers should page the Lab Medicine Attending on-call to arrange with Core Lab.

Methodology

Method: Chemiluminescent microparticle immunoassay (CMIA) by Abbott Alinity i, third generation

Analytical Volume: 0.300 mL serum

Limitations: 

Reference Range

  Age  

TSH

(mIU/mL)

 Critical High

(mIU/mL)
0-<4 d 0.5 - 18.2 >38.5
4 d - <1 mo 0.5 - 6.54 >11.9 
1 mo - <2 mo 0.5 - 6.54  
2 mo - <19 yr 0.47 - 4.17  
>19 yr 0.35 - 4.94  

 

 

 

 

 

 

 

 

TSH transitioned platforms from Ortho Vitros 3600 to Abbott Alinity i on August 8, 2022.

There is a 25% negative bias with the new method.

CPT Codes

84443